This invention is in the field of recovery of soluble, evaporite ore by solution mining between two or more drill holes. More particularly, it involves an efficient method to connect drill holes that recovers a larger proportion of the soluble ore in the ore body than previously recovered by prior art. One basic method involving more than one hole is to drill two conventional, vertical holes into a soluble ore layer. Solution mining is employed in each drill hole creating cavities in the existing ore body. Oil is then introduced into each cavity forming an insoluble pad in the cavity's upper surface and forcing the rapid formation of a flattened cavity. The flattened cavities grow in size until they join together. The formation can then be mined by pumping fresh water into one drill hole and removing saturated ore solution from the other drill hole. Using this method, both drill holes must be completed for individual mining operations and the process to achieve coalescence is slow.
Another method is to drill two conventional, vertical holes spaced a distance apart from each other. One or both of the drill holes is fractured using a high pressure procedure frequently employed by the petroleum industry. 1f the fracture procedure opens a passageway between the two drill holes, water can then be pumped down one drill hole and saturated ore solution can be removed from the other drill hole. ln this method there is no way to control the direction of fracture. Therefore, to insure success, the holes must be drilled closely together. Even if the holes are drilled closely enough together to connect by fracturing, the resulting cavity formation is small and the total saturated ore recovery is diminished.
Still another method is to locate the positions at which two holes spaced a distance apart from each other can be drilled down to the soluble ore body. One of the holes is drilled vertically (conventionally). The other hole is drilled from a point on the surface at a selected distance. This hole is deflected as it is drilled in the direction of the conventional hole. The base of the deflected drill hole then approaches the base of the conventional drill hole. The soluble ore body is fractured by the force from a liquid under high pressure, such as a saturated salt solution, injected down one or both drill holes to obtain a fissure tying together the bases of the two drill holes. If the fracture attempt is unsuccessful, the deflected hole is drilled further toward the bottom of the conventional hole. One or both of the drill holes is again fractured to obtain interconnection. If interconnection is not achieved, the drill holes are individually solution mined to form cavities. When the cavities grow until they join, the soluble ore body is mined by pumping fresh water down one drill hole thereby forcing saturated ore solution out of the other drill hole.
Another disadvantage of these previous methods of connecting two holes is that more holes must be drilled to extract soluble ore from a given area than in the present invention, thereby adversely affecting the economics of the procedure. The present invention results in fewer drill holes, more accurate connection of said drill holes and ore recovery from a larger area of a mineral-bearing stratum resulting in lower, overall production costs than the prior art.